Aircraft: EC130
Phase of flight: Cruise
Anomaly: Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter VFR In IMC

The crew and I just completed a scene flight and were at the hospital. I refueled the aircraft and double checked weather prior to making our return leg to base. All weather reporting stations along our route were all reporting VFR. The closest weather reporting station to our base; was reporting winds 240 at 8 knots; 10 SM visibility; ceilings 9;000 feet scattered; temperature 75 degrees; dew point 64 degrees; humidity 84%; and about 16% illumination. Winds at 1;000 feet AGL was 250 26-28 knots. We departed to the northeast enroute back to base at 2;000 feet MSL; which is a 20 minute flight.Approximately 15 minutes into the flight I noticed some small patches of fog below us at about 500 feet AGL. Our route takes us along the river; and we were approaching a power plant with several bright lights. Once we got to the power plant; the crew and I realized it was very hazy and I decided to deviate from our route and head northbound toward a local Airport. I could still see ground lights and cars driving on the roads. Weather wasn't looking much better to the north; so I made a slight left turn toward the northwest to attempt to get away from the river. I also elected to start a climb in the event we went in Inadvertent Instrument Meteorological Conditions (IIMC). I referenced the GPS and we were 11.3 NM south of the airport now at 2;500 feet. I already had the UNICOM frequency tuned in so I attempted to activate the airport lighting via radio clicks. I saw no signs of lights to the north; and ground lights were deteriorating directly below us. I told the crew we were IIMC and I was coming inside and committing to instruments.I followed the IIMC procedure and got established on a northwest heading. I knew we were in the clouds at this point because the strobe light on the belly of the aircraft was reflecting into the cockpit; so I turned it off. Once I was at my MSA of 4;000 feet MSL; I made a small left turn to 270 and planned on recovering to a county airport as we had just been there previously and I knew it was VMC there when we left about an hour prior. I then switched up Approach control; which was in the standby frequency; and established communication and let them know I was [requesting priority handling] for IIMC. I elected to maintain our company discrete squawk code. I stated my altitude and heading and requested radar vectors to the County Airport. Once they had me on radar he had me turn left to 220 and that would put me on a track toward the airport; which was 14 miles away. After flying this track approximately 5 minutes we broke out of IMC conditions. I told ATC that I was now VMC and had the Airport in sight; but was going to stay committed onto the instruments until I got closer. I told ATC I requested to get set up for the ILS into the county airport for planning purposes. I then descend down to glide slope intercept altitude of 2;500 feet as I was still currently VMC and wanted to make sure I could stay that way at a lower altitude. Approach then advised me that they knew I said I had the airport in sight; but wanted to confirm and the Airport was 12 o'clock and 5 miles. I stated that indeed I had the airport in sight and could cancel the clearance and descend down to the airport VFR. We landed at the airport with no other issues.Not much we can do to remedy this issue; except add more accurate weather reporting stations; especially in known troubled areas. An EC130 helicopter pilot reported he unexpectedly entered IMC after doing a due diligence weather preflight which indicated VMC to his base airport. An IFR clearance was obtained enroute.